One particular type of a stacked injection molding tool which is disclosed in EP 1 957 254 A1 (Boucherie) has a center mold block in the form of a cube defined by four peripheral faces and a pair of spaced end faces joining the peripheral faces along peripheral edges, and a pair of opposed outer mold blocks. The center mold block has two of the peripheral faces forming parallel opposed molding faces joined by two parallel opposed side faces extending perpendicular to the molding faces. The molding faces have parallel partial mold cavities formed therein and the outer mold blocks are each associated with one mold face of the center mold block. The outer mold blocks also each have a molding face with parallel partial mold cavities formed therein which together with corresponding partial mold cavities of the associated mold face of the center mold block form complete mold cavities for molding parts such as brush bodies when the outer mold blocks are positioned close to the center mold block. Each molding face of the center mold block has an accommodation or recess or plural similar recesses for accommodation of movable mold inserts. The mold inserts each have fractions of the partial mold cavities formed therein. When brush bodies or parts thereof are molded by injecting a first component into the cavities defined between the molding faces of the center mold block and a corresponding outer mold block and the mold is opened by separating the outer mold block from the center mold block, the pre-molded parts adhere to the insert or inserts which then serve as holders and can be lifted out of the partial cavities in the molding face of the center mold block. While they are held on the inserts, the pre-molded parts are then moved to one of the two opposed side faces of the center mold block where they are allowed to cool for some time. Then the inserts with the pre-molded parts are moved to the other molding face of the center mold block where a second component is injected. The completed parts, toothbrush bodies in this case, still adhering to the inserts, are then moved to the other side face of the center mold block where they are ejected or removed by a robot.
For moving the inserts with equal indexing steps, a common drive with a pair of turrets is used in which the turrets are mounted on a common axis that crosses the center mold block centrally and parallel to its molding and side faces. For performing each indexing step, the turrets are rotated 90°. Although the common drive for the inserts has advantages in terms of simplicity and synchronization of molding operations and other functions, the inserts must be moved on a circle about the center mold block so that the space requirements are substantial.